Vibrator apparatus



July 17, 1934. 1 J. K. cLAPP Er AL VIBRATOR APPARATUS Filed Oct. 29, 1931 ....Av. n I HR.

Affomey fnl/n t ors Chas. .E Worf/7er? Patented `luly 17, 1934 i UNITED STATES PATENT OFFICE VIBRATOR APPARATUS James Kilton Clapp, Auburndale, and Charles Elmer Worthen, Boston, Mass., assignors to General Radio Company, Cambridge,l Mass., a corporation of Massachusetts Application October 29, 1931, Serial No. 571,930

12 Claims. (Cl. T11-327) The present invention relates to electromeaway, for clearness; and Fig. 2 is a similar perchanical vibrators, and more particularly to piezospective of the crystal holder illustrated in Fig. 1. electric crystals, and to supports and holders A rectangular quartz plate 2 is illustrated in therefor. Fig. 2 inserted between parallel conducting elecn I Piezo-electric crystals, while vibrating, have a trodes 8 and 12, suitably connected in an electric tendenCy t move bodily from side to side between circuit (not shown). If it rests freely between their electrodes. This is undesirable, because the electrodes 8 and 12, it has a tendency to slide tending to Cause erraticl Changes in frequencyfrom side to side during its vibrations; andif it Attempts t0 Center the Crystal by engagement is clamped carelessly, its vibrations will be inter- With its periphery are not Wholly satiSfaCtOry, fered with. According toa feature of the present 65 because the dimensions of the periphery Change invention, a new and improved construction is periodically with the vibratory expansions and provided for holding the Crysta1 plate against contractions 0f the Crystal- Attempts to Clamp bodily movement out of the position in which itV the crystal against movement, 0n the other hand, is fixed, without interfering with its vibrations.

l5 might interfere With its free Vibration- The electrodes 8 and 12 constitute one arm 70 An obl'eot ofthe invention is t0 provide a new each of two right-angular members, the other and improved noiding device for an eleotromeamis of which are disposed in Contact with the Chanlal VibIatOr 0f the abOVe-fCleSClibed Chal'- insulating base 17 The saidother arms are each acter. Y constituted of projections 18, 19, and 21, corre- 20 Another objeCt is to provide a new and imsponding projections of the electrodes being 75 proved holding device that, while positively prealined with each other, In the aiined slots thus venting the Vibrator from moving bodily, permits formed between the projections 19 and 20 are it to vibrate freely. disposed two blocks 9 and 15, adjustably secured Even if the Crystal Were to be held against to the base 17 in any desired manner, as by screws bodily movement, the riCtiOn of its bodily C011- 22 disposed in elongated slots 27 of the insulat- 80 tact with an adjacent surface of relatively large ing base 1'7 Screws 5. and '1ry threaded in the area also tends to introduce frequency changes, blocks 9 and 15, extend toward each other through and a further ObJ'eCt 0f the invention, therefore, alined openings 4 in the electrodes 8 and 12. is to obviate Such frCtion, partiCularly at the The crystal plate 2 is clamped at opposite points vibrating portions 0f the Crystal. 1 and 3 by the ends ofthe screws along small With the above ends in vieW, a feature of the medial areas corresponding, for example, to nodes invention contemplates a new and improved deof movement; or the points 1 and 3 may be dis.. vice for holding the vibrator nodally and, in parposed along the electric axis of the crystal where tieular, at points along the eleetrio aXiS of the there is likewise small Vibratory movement. Be-

piezo-electric crystal. The vibrator may thus be ing thus supported at the stationary points 1 90 held at the Said points entirely out of Contact and 3, and spaced freely from the electrodes, the. with any other points or Surfaces- The holding crysta1 is free to vibrate, without restriction, acmembers may be adiustable- The Crystal eleocording to the desired mode of vibration which trodes may be adjustable independently of the may, for example, be along the direction of the 40 holding members. d longitudinal axis of the crystal plate, that is, 95

The vibrations 0f the Crystal are accompanied along a mechanical axis of the quartz crystal. by air vibrations that, in turn, reaCt upon the Indeed, the invention is particularly adapted for Crystal. after reflectiorl from Such Objects an? the use Crystal bars or rods Vibrating nl the wallsof the Crystal mounting- It is accoqmgly transverse mode at the lowest frequency. It is a further 'object 0f the invention to prfwlde a thus impossible to introduce frequency errors 100 new and improved pame'plate mechamsni for caused either by friction or by changes in posiminimizing the undesn'able eects of such au re' tion of the crystal with relation to its electrodes. flections- The degree of nodal pressure may be adjusted Ciber and further oblect? vlnnl be xsllne by threading the screws in the blocks 9 and 15 105 penelfggna Ealing) particu ar y pom e ou so as to hold the crystal with any desired degree m of tightness, and yet so as to introduce the least The invention will now be explained in connec energy loss from the vibrating crystal to its sup tion with the accompanying drawing, in which Fig. 1 is a perspective illustrating a preferred emports- Damping 0f the Vibrating Crystal 1S thus bodiment of the invention, parts being broken reduced to the minimum. Pads 6 may be inter- 110 posed between the ends of the screws and the crystal.

Provision is made for adjusting the excitation of the crystal by adjusting the electrodes 8 and 12 towards and from the vibrator along a line parallel to the line joining the points or small areas 1 and 3. To this end, screws 23 are disposed in the slots 24 between the projections 18 and 19 and between the projections 20 and 21, respectively. The screws 23 extend through the alined slots formed between these projections and into the base 17. The adjustment of the electrodes is thus effected without disturbing the supporting screws 5 and 7 or the crystal held thereby.

Supports 29 are disposed on the base 17 near the ends of the crystal and are adapted to be adjusted towards and from the crystal ends by angle plates 31 fixed to the supports 29 at 33V and having elongated openings 35 adapted to receive screws 37 that are threaded into the base 17.

'I'he supports 29 each carries a threaded shaft' 39 the end of which supports a baille plate 41. The baille plates 41 are disposed parallel and near to the end faces of the crystal, where-the amplitude of vibration is greatest, and where the consequent production of air or other gas supersonic Waves is correspondingly greatest. The baille plates 41 may be adjustably threaded on the shafts 39 or, as shown, they may be integralwith these threaded shafts. In either case, the baille plates may be adjusted toward and from, and parallel to, the end faces of the crystal to adjust the air or other gas gaps between the baille plates and the crystal ends. In practice, the distance between the ends'of the crystal and baille plates will preferably be a quarter wave-length of the radiation in the atmosphere, or an odd multiple thereof.

It is thus rendered possible to adjust the electrodes 8 and 12 toward and from the sides of the crystal, and the baffles 41 towards and from the .sonic air waves from thi.L ends of the bar, with consequent important reduction in the effective damping of the bar. A greater frequency stability is obtained from the operation of the bar at the preferred spacings, as the frequency changes caused by supersonic waves reflected from nearby surfaces and impinging on the ends of the bars are eliminated. There is -a substantial reductionin the effects of air pressure on the frequency of the bar, since the baille air gaps remain in suitable adjustment, when once properly fixed, for varying air pressures. There is a substantial reduction in the effects of temperature on the frequency of the oscillator controlled by the vibrator because of the prevention of reaction from surrounding objects through supersonic air waves reflected back from the crystal in varying phase as the wave length of the air waves alters with the temperature. Finally, there is a substantial reduction in the changes in frequency of the said oscillator due to the lowered decrement of the crystal which is the prime frequency controlling element.

It is found, in practice, that this crystal mountseparate from vthe housing and may be adjusted independently of the housing. It is thus possible freely to adjust the baffles to t the requirements of any crystal frequency without regard to any housing in which the crystal and its holder may be contained. The effects on the crystal performance that would otherwise be produced by the reflected supersonic air or other gas waves may thus be wholly eliminated, irrespective of the geometrical shape or size of the housing walls or other surrounding objects. The crystal operates wholly independently of the housing in which it is placed.

The walls 49 of the housing may be of heatinsulating or attenuating material, like asbestos, disposed between layers or walls of heat-distributing material, like aluminum, having a relatively low heat capacity and high conductivity, and maycarry heating resistors 51, adapted to be connected into and out of an electric circuit (not shown) by a mercury switch 53.

The housing 47 is disposed in a second or outer housing 55 the walls 57 of which are likewise constituted of one or more layers of heat-insulating material carrying heating resistors 59. The temperature of the second housing is similarly maintained within predetermined limits by a. second mercury switch 61.

It will be noted that the thermostatic switches 53 and 61 are disposed outside the spaces the temperatures of which they regulate, though preferably in intimate contact with the aluminum walls of the corresponding housings, preferably in aluminum pockets 62 secured to the aluminum Walls.

An outermost housing 63 is provided, also of heat-insulating material, such as balsa wood. The housing 63 is surrounded by a Water tank 65 into which water may be supplied by a water pipe 67 through a valve 69. An overflow is shown at,71. A weight 73 normally keeps the valve 69 closed. When the temperature gets high enough, a mercury switch 75 will close a circuit 76 to energize a solenoid coil 79, thereby acting to open the water valve 69. The mercury switch 75 may be set for an air temperature just below that at which the temperature-control unit fails 'to function,'-say, 95 F. The water will naturally be at lower temperature than the airand will thus allow sulcient loss of heat from the unit to permit the thermostatic switches 53 and 61 to effect their contact.

Access to the units may be obtained in any desired way, as by hinging the tops to the side walls oi' the respective housings, or arranging the tops to be completely removable.

The present application is directed to the oscillator-holder assembly. The temperature-controlled, enclosing structure illustrated herein is covered by a divisional application, Serial No. 615,213, filed June 3, 1932.

It will, of course, be understood that the invention is not restricted to the exact embodiment thereof that is illustrated and described herein, as modifications may be made by persons skilled in the art, and all such are considered to fall within the spirit and scope of the invention, as dened in the appended claims.

What is claimed is:

1. Apparatus of the character described comprising a piezo-electric crystal, electrodes for the crystal, means independent of the electrodes for supporting the crystal at two points, and means for adjusting the electrodes along a line parallel to the line joining the points.

2. Apparatus of the character described comprising a piezo-electric crystal, two supports having portions of relatively small area for holding the crystal at two oppositely disposed points, electrodes for the crystal having portions through which the supports extend, and means for adjusting the electrodes without disturbing the supports.

3. Apparatus of the character described comprising a base, two right-angular electrodes having one arm each in contact with the base and the other arms parallel to each other, means for adjusting the electrodes toward and from each other on the base, the first-named armsV having alined slots, two blocks carried by the base in the slots, the other arms having alined openings, a rod threaded in each block and extending through one of the openings toward the other rod, and a piezo-electric crystal supported by the ends of the rods.

4. Apparatus of the character described comprising a vibrator, means for suppressing supersonics including a pair of baiilesv for the vibrator, and means for adjusting the bailes.

5. Apparatus of the character described comprising a vibrator, means for suppressing supersonics including a baille near each end of the vibrator, and means for adjusting the vgaps between the vibrator and the ballles.

6. Apparatus of the character described comprising a vibrator, a threaded support, a threaded shaft adjustably threaded in the support, and

means for suppressing super-Sonics including a baffle for the vibrator mounted 4on the shaft whereby the baille may be adjusted by threadedly adjusting the shaft.

7. An electromechanical vibrator comprising a freely vibratory body, means for holding the body against bodily movement out of a predetermined position, and means for suppressing super-Sonics including a baffle plate for the vibrator, and means for adjusting the baiiie plate.

8. Apparatus of the character described comprising a piezo-electric crystal, electrodes Aadjacent to the sides of the crystal, means for suppressing super-sonics including baffles adjacent to the ends of the crystal, and means for adjusting the baliles. Y

9. Apparatus of the character described comprising a piezo-electric crystal, electrodes adjacent to the sides of the crystal, means for suppressing super-sonics including baflles adjacent to the ends of the crystal, and means for holding the crystal out of contact with th electrodes.

l0. Apparatus of the character described comprising a housing, a vibrator in the housing, and means for suppressing super-Sonics including a pair of balles for the vibrator in the housing and separate from the housing.

11. Apparatus of the character described comprising a housing, a vibrator in the housing, means for suppressing super-Sonics including a pair of baffles for the vibrator in the housing, and means for adjusting the baffles in the housing.

12. Apparatus of the character described comprising a piezo-electric crystal, electrodes for the crystal, two rigid supports independent of the electrodes having portions of relatively small area for holding the crystal at two oppositely disposed nodal points of the crystal, and pads between the crystal and the rigid supports.

JAMES KILTON CLAPP. CHARLES ELMER WORTHEN.

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